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React Native sticky row and header scroll performance?

I have cobbled together a working version of a Microsoft Excel like "freeze pains" view. The column header scrolls with the content horizontally and the row headers scroll with the content vertically but each is "stuck" in position when the other is scrolled.

You can try the working version here.
It's not optimal as it stutters if you stop a flicked scroll or just swipe around a lot.

The approach uses a couple techniques but the one causing the issue is the synced scroll view.

As outlined here, I've tried setting useNativeDriver: true, which necessitates changing
ScrollView to Animated.ScrollView and
ref={ref => (this.instance = ref)} to ref={ref => (this.instance = ref._component)} but then the synced goes completely haywire.

I'd love ideas on a more optimal approach. How can this be improved?

import React from 'react';
import { ScrollView, Animated, Text, View } from 'react-native';

export default class SyncScrollTest extends React.Component {
  constructor() {
    super();
    this.scrollPosition = new Animated.Value(0);
    this.scrollEvent = Animated.event(
      [{ nativeEvent: { contentOffset: { y: this.scrollPosition } } }],
      { useNativeDriver: false },
    );
  }

  render() {
    return (
      <View style={{ flex: 1 }}>
        <View style={{ flexDirection: 'row' }}>
          <ScrollViewVerticallySynced
            style={{ width: 50, marginTop: 60 }}
            name="C1"
            color="#F2AFAD"
            onScroll={this.scrollEvent}
            scrollPosition={this.scrollPosition}
          />
          <ScrollView horizontal bounces={false}>
            <View style={{ width: 600 }}>
              <View style={{ height: 60, justifyContent: 'center', backgroundColor: '#B8D2EC' }}>
                <Text>
                  I am Column Header!! I am Column Header!! I am Column Header!! I am Column
                  Header!! I am Column Header!! I am Column Header!! I am Column Header!!
                </Text>
              </View>
              <ScrollViewVerticallySynced
                style={{ width: 600 }}
                name="C2"
                color="#D9E4AA"
                onScroll={this.scrollEvent}
                scrollPosition={this.scrollPosition}
              />
            </View>
          </ScrollView>
        </View>
      </View>
    );
  }
}

class ScrollViewVerticallySynced extends React.Component {
  componentDidMount() {
    this.listener = this.props.scrollPosition.addListener((position) => {
      this.instance.scrollTo({
        y: position.value,
        animated: false,
      });
    });
  }

  render() {
    const { name, color, style, onScroll } = this.props;
    return (
      <ScrollView
        key={name}
        ref={ref => (this.instance = ref)}
        style={style}
        scrollEventThrottle={1}
        onScroll={onScroll}
        bounces={false}
        showsVerticalScrollIndicator={false}
      >
        {someRows(name, 25, color)}
      </ScrollView>
    );
  }
}

const someRows = (name, rowCount, color) =>
  Array.from(Array(rowCount).keys()).map(index =>
    (<View
      key={`${name}-${index}`}
      style={{
        height: 50,
        backgroundColor: index % 2 === 0 ? color : 'white',
        flex: 1,
        alignItems: 'center',
        justifyContent: 'center',
      }}
    >
      <Text>
        {name} R{index + 1}
      </Text>
    </View>),
  );

```

like image 348
GollyJer Avatar asked Oct 29 '22 05:10

GollyJer


1 Answers

I've changed your example, instead of using listeners and Animated Event I use the scrollTo method from ScrollView to synchronize the scrolling. I think that listeners are the cause of lag between the rows when you are scrolling.

You can test the changes here.

import React from 'react';
import { ScrollView, Text, View } from 'react-native';
import { Constants } from 'expo'

export default class SyncScrollTest extends React.Component {
  constructor() {
    super();
    this.c1IsScrolling = false;
    this.c2IsScrolling = false;

  }

  render() {
    return (
      <View style={{ flex: 1, marginTop: Constants.statusBarHeight }}>
        <View style={{ flexDirection: 'row' }}>
          <ScrollViewVerticallySynced
            style={{ width: 50, marginTop: 60 }}
            refe= {ref => (this.c2View = ref)}
            name="C1"
            color="#F2AFAD"
            onScroll={e => {
                if (!this.c1IsScrolling) {
                  this.c2IsScrolling = true;
                  var scrollY = e.nativeEvent.contentOffset.y;
                  this.c1View.scrollTo({ y: scrollY });
                }
                this.c1IsScrolling = false;
              }}

          />
          <ScrollView horizontal bounces={false}>
            <View style={{ width: 400 }}>
              <View style={{ height: 60, justifyContent: 'center', backgroundColor: '#B8D2EC' }}>
                <Text>
                  I am Column Header!! I am Column Header!! I am Column Header!! I am Column
                  Header!! I am Column Header!! I am Column Header!! I am Column Header!!
                </Text>
              </View>
              <ScrollViewVerticallySynced
                style={{ width: 400 }}
                refe= {ref => (this.c1View = ref)}
                name="C2"
                color="#D9E4AA"
                onScroll= {e => {
                  if (!this.c2IsScrolling) {
                    this.c1IsScrolling = true;
                    var scrollY = e.nativeEvent.contentOffset.y;
                    this.c2View.scrollTo({ y: scrollY });
                  }
                  this.c2IsScrolling = false;
                }}

              />
            </View>
          </ScrollView>
        </View>
      </View>
    );
  }
}

class ScrollViewVerticallySynced extends React.Component {
  render() {
    const { name, color, style, onScroll, refe } = this.props;
    return (
      <ScrollView
        key={name}
        ref={refe}
        style={style}
        scrollEventThrottle={1}
        onScroll={onScroll}
        bounces={false}
        showsVerticalScrollIndicator={false}
      >
        {someRows(name, 25, color)}
      </ScrollView>
    );
  }
}


const someRows = (name, rowCount, color) =>
  Array.from(Array(rowCount).keys()).map(index =>
    (<View
      key={`${name}-${index}`}
      style={{
        height: 50,
        backgroundColor: index % 2 === 0 ? color : 'white',
        flex: 1,
        alignItems: 'center',
        justifyContent: 'center',
      }}
    >
      <Text>
        {name} R{index + 1}
      </Text>
    </View>),
  );

You can find another example here

like image 58
Mario Mourao Avatar answered Feb 09 '23 00:02

Mario Mourao